Setscrew



M. s, 1938. H. F. GADE 2,135,637

' SET SCREW Filed April 26, 1935' 2 Sheets-Sheet l Invert/#2 H. F. GADE SET SCREW Nov. 8, 1938.

Filed April 26, 1935 2 Sheets-Sheet 2 LJwezzzfor omrao sr rEs' conditions.

Patented Nov. 8, 1938 PATENT OFFICE SETSCREW Harald F. Gadc, Philadelphia, Pa., assignor to Application April 26, 1935, Serial No. 18,487

8 Claims. (Cl. 151- -22) This invention relates to improvements in set screws, and while applicable in principle 'to set screws of any type has an application of particular importance to so-called hollow and headless set screws. g

One of the principal disadvantages of set screws generally has resided in the diiilculty of providing an adequate lock to hold the screw securely in position and to prevent the natural tendency of the screw to loosen under operating A principal object of the present invention is to provide a set screw embodying in its structure simple. and eii'ectivemeans for lockingthe screw in'positlon.

Another object of the invention is to provide a set'screw of the stated character, wherein the .;locking means, while 'eifectiveto 'maintain the screw in position under normal conditions, will permit retraction of the screw when necessary, and wherein the'said locking means is of such character as not unduly to complicate or increase the cost of the manufacturing process.

In the attached drawings:

' Figure 1 is a view in perspective of a set screw made in accordance with my invention;

Fig. 2 is an enlarged fragmentary sectional perspective view illustrating the lock thread formation;

Fig. 3 is a perspective view similar to that of Fig. 1 showing a preferred embodiment of my invention;

Fig. 4 is an enlarged fragmentary perspective view of the thread formation shown in Fig. 3;

Fig. 5 is a fragmentary sectional view of the thread shown in Figs. 3 and 4; and

Fig. 6 is a fragmentary sectional view illustrating a further modification within the scope of the invention.

With reference to Figs. 1 and 2 of the drawings, it will be noted that in the set screw therein illustrated, which is of the hollow and headless type, the threads fat the inner or working end are of normal formation, and that a relatively small section 2 of the thread at the outer end of the screw is in effect serrated and to a limited degree upset, so that at the peripheral. edge the threads in this section are at least in part of greater width than the normal thread in the same circumferential plane.

g In a preferred method of manufacturing set screws in accordance with my invention, I produce the screw by normal machine operation and in accordance with the standard practice. I then,

as illustrated in the drawings, slightly deform a relatively short section of the thread at the outer or socket end by means of a simple knurling operation. As illustrated, this knurling operation has the effect of serrating and, at the same time, upsetting the peripheral edges of the thread, with the formation of beads 3 at the edges of the serrations and on both the inner and outer faces, 4 and 5, of the thread. By this means, the effective thickness of the peripheral edge of the thread within the knurled section is made somewhat greater than the thickness of the corresponding portion of the normal thread, and this increased thickness is confined primarily to a narrow area at the peripheral edge of the thread and at each side thereof following the irregular path of the knurlings. When a screw of this novel construction is entered in the threaded hole provided for its reception, the normal threads extending over the major portion of the screw from the inner end mesh with the threads of the hole in normal manner, whereas the knurled section of the thread, by reason of its abnormal form, tends to bind within the threads of the hole so that the screw is effectively locked in the final adjusted position. While the set screw as described will remain locked in position under all normal conditions, the screw may readily be removed if occasion requires. It will be noted that by reason of the fact that the locking device is confined entirely to a relatively small section at the outer ends of the threads, the inner and major portions of the threads remain unchanged. My I invention accordingly involves no undesirable destructive effects upon the major portions of the 35 threads either of the threaded hole or of the set screw.

A preferred embodiment of my invention is illustrated in Figs. 3, 4, and 5. In this case, the serrations, instead of being parallel with the longitudinal axis of the screw, are inclined to said axis, and preferably the serrations are inclined from the inner surface 4 of the thread toward the outer surface 5 in the direction in which the screw is rotated when released. When these diagonal serrations are formed by knurling, it is possible to obtain an upset formation correspondin: to that shown, wherein the bead 3a and hence the major increased thickness of the thread caused by the upsetting action is located at one side or the respective serrations, namely, that side which slopes inwardly toward the rising portion of the helix as viewed in Fig. 3. I prefer also to confine the "upset to the outer face of 2s; v r r furl thread as illustrated, andthis may be accom- V plished by a machine operation subsequent to the kn'urling operation to remove the upset nu and bead-from the lower surface 01' the thread. In

this manner, I provide a screwiin' which the characteristic upset thread formation is confined v to the outer surface of the thread and takes the form substantially ot a series 01' beads extending diagonally inward from the peripheral, edge of T.

the thread and toward those portions of the helix which lead when the, screw is backed out oi the threaded. opening. with this arrangement the smooth inner surfaces or the stantially normal solid 7 thread find a subbearing on the threads of the tapped hole while the binding action occurs between theouterupset surface the thread of the screw and the reverse surface of the receiving depth and to one'face onlyof-the thread.

.. element. I v a 4. Asanew article of manufacture,"a:screwj l thread. Thelocking action in this form of screw emolent;

; v rt'wmbe apparent that the invention in prin ciple may find other embodiments than those illustrated in Figs; 1 to 5 A soniewhat similar efiect may be obtained, for example. by a simple upsetting of the peripheral edges of the threads ,within' the limited area described through the 'medium,*ior'example, or a smooth-iaced'roller.

" The knurling'however, is preferred both by reason of the relative mechanical simplicity of the knurling operation as compared with a corresponding operation with a smooth roller, and by reason further that the upset formation obtained by the knurled tool is'more eflectivein thelocking has; been found to be relatively eflectiveand function. In Fig. 6,1 have illustrated! softenerv modification wherein the serrations orw l eesses at the periphery of the thread are in effect 'sawtoothed and project outwardly in a direction reverse to that in which'the set screw is turn'edier tightening. There may be otherinodihcations within the sc'opelof the irlpentlon.

I claim: 1 1. As a new article of manufacture, a screwthreaded element having at least a portion oi its being confined to a small thread upset at the crest by knurling, being conflnedto a small part onlyoi thetotal a the outer-end oi the screw.

thread contour.

at thejcrest bf'knurling, said upset depth oithethread." v t 2. As a new article ct manuiacture', a'screwthreaded element having at least a portion of its said upwt part only of the total ,3..As a'newarticleot manufacture, a screw- I threaded element having at least a portion or its.

thread upset-at the crest. by knurling. said mun ings being inclined threaded element having at least a portion of its thread transversely'expanded at the' crest 'said manded portion being adapted toiam in anjor-f mai thread in which said element ismatedto thereby relatively lock said threads. 1

a 5. As a newartlcle oi mamifacture, aset-screw having a portion or its thread transversely sexpanded at the crest, said expandedportionbeing to the longitudinal axiso! said confined to a section o'fthe. adjacent the outer end oi said screw, I

8. As anew artielelot-manidacture, a set screw having a portion for its threadtransversely ex-- pended at thegcrest hy kziurling. aid knurlings being confined to a section'of the thread adjacent- "mis alnew' a v threaded .elemen'thaving at least aportion of its said. element *is' die of manufacture, 'asci-ewe" "thread-transversely expanded at the crest by l expanded portion being adapted to my normal thread in which :mated tbgthereby' relatively lock'sa'id threads.

",SaIAs' a new article 01 manuiacture, a screw- Y threaded elementhaving at least a portion of its thread provided with spaced recesses, the edges or which are defined by narrow ridges projecting outwardly beyond the conflnes oi vthe normal 1'. cabs. 

